Track type drafting machine



Aug. 7, 1962 J. A. HlsLoP 3,047,954

TRACK TYPE DRAFTING MACHINE Filed Deo. 8, 1958 2 Sheets-Sheet 1 Aug. 7, 1962 Filed Dec.

"IHHIII" J. A. HISLOP TRACK TYPE DRAFTING MACHINE 2 shets-sheet 2 5 l Clam/4.375,09 7 JNVENTOR.

United States Patent O E as 3,047,954 TRACK TYPE DRAFTENG MACHINE John A. Hislop, Costa Mesa, Calif., assigner to Varel Products Inc., Costa Mesa, Calif., a corporation of California Filed Dec. S, 195e, Ser. No. 778,946 2 Claims. (Cl. Ba-476) This invention relates to drafting machines which carry a drafting instrument for movement in translation over the surface of a drafting board or the like. The invention relates more particularly to such drafting machines that maintain parallelism of the drafting instrument by means of two mutually perpendicularV track structures.

A pn'mary object of the present invention is to overcome certain disadvantages of previously available drafting machines of that general type.

The invention provides track structures of highly efficient form, affording high rigidity 'and accuracy with relatively light weight. Moreover, the novel track structure of the invention presents a vsmooth outer surface, unencumbered by sharp edges and projecting parts.

The invention further provides carriage structure that permits the active parts of the carriage guiding mechanism to be effectively fully enclosed within the interior of the track structure, where they are protected from dirt and from possible damage. Also, the frame structure of the present carriages is substantially hidden from view behind the track itself, and thus protected from damage, dirt and accidental displacement from the desired position.

The invention further provides improved support and guide structure for the carriages, facilitating accurate adjustment and ample range of movement over the drafting surface.

A full understanding of the invention, tand of its further objects and advantages, will be had from the following description of a preferred illustrative manner of carrying it out. Particulars of that description, and of the accompanying drawings which form a part of it, are intended only as illustration and not as a limitation upon the scope of the invention, which is defined in the appended claims.

In the drawings:

FIG. l is a front elevation representing an illustrative drafting machine in accordance With the present invention, with the drafting table ,illustratively shown in vertical psition;

FIG. 2 is 1a side elevation, `corresponding to FIG. l;

FIG. 3 is a section generally on line 3 3 of FIG. l, at enlarged scale;

FIG. 4 is a fragmentary section on line 4 4 of FIG. l at the scale of FIG. 3;

FIG. 5 is a fragmentary section on line 5 5 of FIG. 3;

FIG. 6 is a fragmentary section on line 6 6 of FIG. 3;

lFIG. 7 is a fragmentary section corresponding to a portion of FIG. 3 at further enlarged scale;

FIG. 8 is a section on line 8 8 of FIG. 3; and

FIG. 9 is a section on line 9 9 of FIG 3.

In the drawings, the numeral 2@ represents a typical drafting table, drafting board, or the like, with upper edge 21, lower edge 22 and left and right side edges 23 and 24, respectively. The working surface of table is indicated at 25. Working surface 25 is shown illustratively in vertical position. However, it may typically be horizontal, or may be inclined at any desired angle by means of adjustable support structure. The support structure may be of conventional type `and is not explicitly i1- lustrated.

A main track, represented at 3l), is mounted on drafting table 2l) by means of the left and lright corner brackets 32 and 34, respectively. Track 30 may, in general,

3,047,954 Patented Aug. 7, 1962 ICC be mounted on the drafting table in any desired orientation, but is ordinarily parallel to upper edge 21 of the table, and will be described for deliniteness. When the drafting table is inclined, the length of main track 30 then remains horizontal. For that reason, it will be referred to for convenience as the horizontal track, but without thereby implying any limitation upon the invention.

The main or horizontal carriage, indicated generally at 4d, is movable in translation along the length of main track 30, by means to be more fully described. A transverse elongated support, represented as the track 50, is mounted on carriage 4t) by means of the bracket structure 42', and extends perpendicularly to the length of main track 30. Transverse track 50 will be referred to as a vertical track, since it is ordinarily parallel to vertical lines on working surface 25. And when that surface is positioned in a vertical plane, as in the drawings, track Sil is also vertical in the sense of being parallel to the direction of gravity.

A second carriage 60, which may be referred to as the vertical carriage, is movable along the length of vertical track Sd and carries a bracket 62 on which any desired structure may be provided for carrying a drafting instrument. An illustrative drafting head assembly is represented schematically at 26, carrying two mutually perpendicular straight edges 27 and 2S. Head assembly 2o, which may be of conventional type, typically permits convenient rotational adjustment of the carried drafting instrument about an axis 29 which is perpendicular to working surface 25. For example, head assembly 26 may be similar in general form to the structure disclosed in FIGS. 5, 6 and 7 of United States Patent 2,394,344, issued to Jard B. Wallace on February 5, 1946.

In the present illustrative embodiment of the invention, each of the tracks 30 and 50 comprises a unitary channel member of uniform transverse section. The form of that channel provides advantageous economy of construction and assembly, convenience in use and accuracy of operation. As is clearly shown in FIGS. 4 and 7, for example, each track channel comprises typically a relatively wide web portion 52, which lies in a plane parallel to work surface 25, and side flanges 54, which extend rearwardly from the web in the direction of a perpendicular entering that surface. The rear edge portions of flanges 54 curve toward each other, as at 55, forming a corner edge at 56. The web and flanges thus partially enclose a chamber, indicated schematically at 57, which typically extends the entire length of the track. In the present embodiment, chamber 57 is closed at both ends of each track by the closure plugs 39, which may be of a suitable plastic material, for example, so formed as to be insertable in the end of the track with a pressure fit. Chamber 57 is then open only via the elongated mouth that is formed at 58 between the edges 56 of the channel flanges.

In accordance with one aspect of the invention, the track channel members are so formed that the outer faces of the web and flanges form a unitary, smoothly curved surface 59, which extends continuously and without any sharp edge or abrupt discontinuity from one of the corner edges 56, already desciibed, to the other. The smooth curvature of that surface, extending inthe present preferred ernbodiment through substantially 360 of angle, is convenient and comfortable to the touch during use of the machine. It has the further important advantage of resisting the accumulation of dirt and dust. Moreover, the smooth external form of the tracks minimizes the danger that the instrument will be accidentally shifted from the position in which the operator has set it. For example, the operators hand or sleeve or other moving object can easily slide over the track from one side to the other, and does not tend to catch and displace the track as is the case with previously available track structures.

The described track structure may be viewed alternatively as comprising a hollow tube, somewhat flattened to form an oval section with major axis parallel to working surface 25, and having a longitudinal slot at 53 which extends the entire length of the track.

Within the chamber 57 of each track member are formed longitudinal guide surfaces, which may be of any suitable type. As illustrated, two guide flanges 70 are provided, which extend in mutually opposed spaced relation in a common plane from the respective channel flanges. The plane of guide flanges 7@ is preferably weil within chamber 57, that is, between web portion 52 and the plane delined by mouth edges 56. The longitudinal rib 7l, which is provided midway of the inner face of web 52 in the present embodiment, may be omitted if its stilfening action is not required.

Horizontal track 3@ is mounted on drafting table Z@ by bracket structure that positively defines the longitudinal axis of the track, while preferably permitting ree pivotal movement about that axis. That mounting permits lifting the drafting head and vertical track clear of the work surface, so as to facilitate changing drawings. For that purpose, the brackets 32 and 34, which are iixedly mounted on table 2t) as by the screws 36, carry the pivot pins 33 and 35, respectively. Those pins are mounted in the free ends of the brackets in mutual alinement, and preferably extend away from each other. The pins are rotatably received in the respective fixtures 37 and 38, which are mounted at opposite ends of track 30 in longitudinally adjustable positions. As shown, the fixtures are slidingly received between the channel flanges of the track, positively engaging guide flanges 7th. They are clamped in the desired longitudinal position, as by the screws 42 and clamping members 43, which fit inside the guide flanges (FIG. 4).

Brackets 32 and 34 are so formed, as clearly shown in FIGS. 2 and 4, for example, that the axis of pivot pins 33 and 35 is offset back of the plane of work surface 25. That offset is sufficient that the entire horizontal track lies back of that plane, and therefore does not interfere with any instruments or papers that may extend from the work surface beyond its upper edge 2l. Left bracket 32 is also odset horizontally, so that its pivot pin 33 is positioned well outside of the left hand edge 23 of the drafting table, as shown clearly in FIG. 1. That arrangement facilitates full use of the available work surface 25.

The two carriages dll and 6@ are preferably similar in general construction, embodying further important aspects of the present invention. Horizontal carriage di), `for example, comprises an elongated carriage frame portion 4l, the bracket portion 42, which extends transversely from the frame portion adjacent one end thereof, and guide structure adapted to guide the carriage along track Sti. Carriage frame 41 typically comprises a flat elongated plate that is appreciably narrower than the track member 30, its width being preferably approximately equal to that of channel mouth 58. It is guided on guide flanges '70 of the track channel by three rollers 4d, 45 and d6, which are mounted at longitudinally spaced points of the frame, and which lie within channel chamber 57. The two end rollers engage the guide flange on one side of chamber 7, while the intermediate roller engages the guide ange on the other side of the chamber. The periphery of each roller is made complementary in section to the guide surface, being grooved in the present instance at 47 (FIG. 3), so that the carriage is positively confined to the track, and has only the single degree of freedom corresponding to translational movement along the track.

The rollers 44, 45 and 46 are preferably turned from solid nylon and are freely rotatable on ball bearings 48, which are mounted, in turn, on carriage frame 41 by mounting means which both locates the roller within the channel chamber and provides for accurate adjustment of each of the three rollers transversely of the length of frame 4l. Such mounting means in the present embodiment comprise the eccentric pivot studs 65.

Those studs typically consist of a pin 66 on which the inner race of bearing 4S is carried with a press t; a mounting shank 67, threaded near its outer end to receive nut 64, and provided with a screw driver slot 68 or similar tool fitting beyond the nut; and a spacing flange 69 between the pin and shank portions. The axes of the pin and shank are parallel, but eccentrically offset by one half the total desired adjustment. An offset of from 0.05 to 0.10 inch is ordinarily satisfactory.

Adjustment of the transverse position of either of the end rollers or 46 provides a convenient means for accurately setting the longitudinal axis of vertical track 5@ perpendicular to that of horizontal track 30. After that angle has been properly set, central roller may be adjusted to eliminate any play between the two guide iianges without impeding free translation of carriage 40 along the track.

Carriage 6i) similarly comprises a frame member 61, which extends parallel to vertical track 50 and is narrower than the track and confined to the space directly back of the track and between it and Working surface 25. Bracket 62 extends transversely from frame 61 adjacent the lower end of the latter and in substantially the same plane, the bracket and frame being typically of unitary construction. The frame and bracket thus comprise an L-shaped member, one leg of the L forming the frame and the other the bracket on which head assembly 26 is mounted.

Carriage 6@ is supported on track 50 by the three rollers 7d, 75 and 76 which are typically constructed, arranged and adjustably mounted on frame 61 in a manner similar or identical to that already described in connection with rollers Mr, 45 and 46 of horizontal carriage 40.

Vertical track 50 may be tixedly mounted on horizontal carriage in in any suitable manner. The structure of bracket 42 in the present embodiment affords the important advantage of maintaining the desirable smoothly curved outer surface of the entire track assembly, while permitting the underslung vertical carriage maximum range of travel. Bracket 42, as shown, comprises a sleeve formation which ttingly receives the vertical track channel (FIGS. 3 and 8). The track is releasably locked in place as by the set screws 83. The vertical track preferably extends for an appreciable distance above sleeve 80, that projecting portion of the track being indicated at Si. The length of that projection is readily adjustable by loosening set screws 83. The portion of sleeve Sti and its support bracket opposite channel mouth 5S is cut away, forming an aperture S2. That aperture provides clearance for frame 61 of the vertical carriage and for the roller supporting studs which it carries. Hence, the upward movement of vertical carriage 6i) is not checked when its upper end reaches horizontal track 34'), but may continue until the upper edge of bracket 62 reaches sleeve Sti. That freedom of movement is accomplished without sacrificing the relatively wide longitudinal spacing of rollers 74, 75 and 76; and also without sacrificing the underslnng arrangement of the entire carriage frame.

When the drafting table is in inclined or vertical position, vertical carriage 50, its carried head assembly 26 and drafting instruments 27 and 28, tend to slide downward across work surfaces 25 under the inuence of gravity. The present invention provides particularly convenient and effective counterbalancing mechanism for overcoming that tendency. A connterbalancing mass is mounted in longitudinally movable relation within chamber 57 of vertical track channel 56. Any suitable guide means may be provided for mass 90 to confine it to a portion of chamber 57 that is clear of carriage rollers 74, 75 and 76. As shown, the mass is guided by the rib 7i and by a portion of the inner face of each guide ange 70. Mass 90 is preferably formed of a heavy metal, such as lead, and is provided at its points of contact with acuosa the guide surfaces with inserts of suitable material having a low coeflicient of friction with the track. Those inserts, indicated at 91 in FIG. 9, may comprise, for example, polymerized tetralluoroethylene, which is cornmercially available under the trade name Teflon. A longitudinal clearance groove 92 on the surface of mass 9u facing channel mouth 58 provides clearance for the inner portions of the guide rollers of carriage 60.

Mass 9o is operatively connected to vertical carriage 60 by the flexible cables 93 and 94, which pass over the respective upper and lower pulleys 95 and 96. Those pulleys are mounted within the track chamber 57 adjacent its ends by means of the pulley brackets 97 and 98, respectively. Those brackets are clamped to one of the guide flanges 70 by set screws 99, and are positioned relative to the other guide flange 70 by a tongue formation 100 (FlG. 9). The axis of rotation of each pulley is preferably oblique, providing direct lead of the cable lights to mass 90 and to carriage frame 61, respectively.

Lower pulley -bracket 9% also provides a convenient means for mounting the roller 1418, which is rotatable about an axis parallel to the length of vertical track 50 and supports the lower end of that track in positively spaced relation to Work surface Z5.

The described structure is conveniently adaptable for mounting on a drafting table with main track 30 parallel to one of the side edges of the table, rather than to the top edge as has been illustratively described. For that purpose, a co'unterbalance mass is provided for main carriage 40 and the parts supported thereon. Such a counterweight may slide within channel 30 and may be operatively connected to carriage 4t) in a manner closely similar to the counterbalance structure already described for carriage 60. lf desired, such balancing means may be provided for both carriages.

Means are preferably provided on each of the carria-ges 40 and 60 for releasably locking them at any selected position on their respective tracks. As illustrated, aV horizontal carriage locking screw 102 is threaded in bracket 42 in position to engage the upper edge of horizontal track 30 at a point immediately to the right of vertical `track 50, where its knurled head is conveniently accessible to the right hand of the operator. A vertical carriage lock screw 104 is threaded in the upturned ear 105 of carriage frame 61, in position to engage the left edge of vertical track 50.

I claim:

1. ln a drafting machine, the combination of track means adapted to be mounted on a drawing board or the like parallel to :a horizontal edge thereof, a generally tubular member movable along the track means and extending perpendicularly thereto in parallel spaced relation to the working surface of the drawing board or the like, said member substantially enclosing an elongated charnber and having `a longitudinal slot providing access to the chamber, structure forming a lirst plurality of mutually `opposed longitudinal guide surfaces within the chamber adjacent the slot, carriage means movable longitudinally of the tubular member land comprising bearing means mounted on the carriage means and engaging the guide surfaces within the chamber, structure forming `a second plurality of longitudinal `guide surfaces facing inwardly within the chamber, counterweight means mounted Cil within the chamber i-n guided relation to the last mentioned guide surfaces and freely movable along the inner side of the chamber past the bearing means, pulley means rotatably mounted on transverse axes adjacent the respective ends of the tubular member, and flexible cable means passing over the respective pulley means between the carriage means and the counterweight means, both ilights of the cable means lying substantially within the chamber.

2. In a `drafting machine, the combination of an elongated track member of generally oval channel section, means for mounting the track member parallel to one edge of a drafting 'board or the like and below the working surface thereof, with the open side of the channel facing oppositely to said surface, a first carriage, means mounting the carriage directly below the track member for movement longitudinally thereof and comprising structure forming ya plurality of longitudinal guide surfaces within the track member `and bearing means mounted on the carriage `and engaging the guide surfaces, an elongated support member of generally oval channel section, means mounting the support 4member on the carriage and oomprising an elongated bracket having one end mounted on the carriage and extending upwardly therefrom `on the side of the track member remote from the drawing board or the like, the other end of the bracket being mounted on the support member `at `a point intermediate the length thereof, one end of the support member extending from the bracket in spaced perpendicular relation above the track member and in spaced parallel relation above the working surface of the `drafting board yor the like with the open side of the support member channel facing said surface, the bracket being apertured adjacent the channel opening, a second carriage comprising an elongated frame portion `and an arm portion extending transversely therefrom adjacent one end, means mounting the second carriage for movement longitudinally of the support member and comprising structure forming la plurality of longitudinal guide surfaces within the support member 'and bearing means mounted on the carriage frame portion and engaging those guide surfaces, said frame portion directly underlying the support member with its other end directed toward said bracket, a drafting head assembly mounted on the carriage arm portion land adapted to carry a drafting instrumen-t, the second carriage being freely movable along the support member to a position where the other end of the carriage frame portion projects between the support member and the track member and through the bracket aperture with its lbearing means engaging the guide surfaces within said other end of the support member beyond the bracket, whereby the drafting head assembly is movalal closely adjacent said edge `of the drafting board or the References Cited in the le of this patent UNITED STATES PATENTS 627,665 Braun June 27, 1899 1,149,120 Fortune Aug. 3, 1915 2,102,636 McDonald Dec. 21, 1937 FOREIGN PATENTS 648,123 Great Britain Dec. 28, 1950 305,144 Switzerland Apr. 16, 1955 741,016 Great Britain Nov. 23, 1955 550,141 Italy Oct. 22, 1956 

